The principle thrusts of these projects are to evaluate bone blood flow and intravascular pressure in fracture healing, simultaneously measure bone blood flow and rate of deposition of bone seeking minerals in bone diseases characterized by abnormal remodeling (i.e. hyperparathyroidism and hyperthyroidism) and to establish the physiologic relationship between cortical and marrow blood flow in bone. Studies now near completion indicate that a venous tourniquet applied to the fore limb or hind limb of a dog will increase bone remodeling and accelerate fracture healing in mature dogs. Separate studies are planned to make dogs hyperparathyroid with the object of measuring mineral transport. These studies will have a second purpose of determining whether marrow and cortical bone blood flow are joined in series or parallel.